This invention relates to an image-receiving sheet which is used in combination with a heat transfer sheet, for performing recording corresponding to information by heat transferring the dye or pigment in the heat transfer sheet.
The heat transfer recording system has been widely utilized as the recording system in a printer such as that in a computer, word processor, and other devices. In recent years, attempts have been made to use a heat-transfer sheet having a heat transfer layer containing a sublimatable dye provided on the surface of a substrate such as polyethyleneterephthalate in combination with an image-receiving sheet and perform overlayed recording of cyan, magenta, yellow, etc. thereby to accomplish recording of images of natural color photographic tones on said image-receiving sheet. This technique is being utilized in the case of, for example, recording an image directly on a CRT display.
As such image-receiving sheets, those with a construction having a receiving layer provided on the surface of a resin with high heat resistance such as polyethyleneterephthalate, non-foamed film of polypropylene type resin, or a synthetic paper using a polyolefin type resin or a polystyrene type resin as the base material have been known in the art.
However, an image-receiving sheet using polyethyleneterephthalate, etc., as the substrate may incur a lowering in its transferred image density due to high rigidity and low thermal insulating property of the substrate, and yet sometimes smooth sheet delivery may not be obtained. Consequently, there have been the drawbacks such as printing drift or color drift occurring when overlayed printing is repeated several times as in color printing, whereby transferred images of high sharpness could not be obtained.
Also, while printing according to the heat transfer system has been done by means of a heating printing means such as a thermal head, since the heat during transfer is applied only from one direction of the sheet in the image-receiving sheet of the prior art, the substrate of the image-receiving sheet curls so that the receiving layer side is on the concave inner side, thus resulting in the drawback of poor transfer.
Further, after a desired image has been once transfer recorded on a receiving layer by heating the heat transfer sheet as described above by means of a thermal head, the image may be transferred onto a transferable article such as telephone card in some cases. When used as transferred on a transferable article, a transparent image-receiving layer is provided on a transparent substrate, and after forming, for example, a reverse image on the image-receiving layer, heat transfer is carried out directly on an article, or through an adhesive sheet in the case of a cloth or the like. The transparent substrate may be permitted to remain as it is on the article to provide a protective layer or, alternatively, it may be peeled off to make the image-receiving layer the protective layer.
However, with a sheet having only a transparent receiving layer provided on a transparent substrate, there is the problem of difficulty of detecting the state of sheet delivery in the heat transfer device. Further, in transparency of the prior art, a support comprising a polyethyleneterephthalate film, or the like containing generally titanium white, etc. has been used as laminated, freely peelable on the back surface of the substrate for the purpose of reinforcement of the sheet. Thus, in the image-receiving sheet for transfer onto a transferable article having a support in laminated state on the substrate back surface, the transparent substrate is generally as thin as about 6 to 25.mu., but since the image-receiving sheet is further laminated on the back surface with a support comprising a non-foamable resin, the rigidity as a whole becomes too high.
For this reason, the actual contact dot area between the heat transfer sheet and the image-receiving sheet becomes smaller as compared with the dot area heated by a thermal head. As the result, the density of the transferred image is low, and yet delivery of the image-receiving sheet during heat transfer in the transfer device cannot be conducted smoothly by means of the transfer device, whereby there has been the problem of printing drift or color drift in the case of performing overlayed transfer repeatedly as in color transfer.